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Multiple GPIOs

  • Hi,

    As a newbie to the IoT, and new to Onion, would like to know few questions after reading the docs.
    a) For Omega2 only 12 GPIOs available, does that means only 12 different devices can be connected but not more than that. Eg., 6 LED lights, 6 Switches each, if the use case is to have Switch for each LED.
    b) Where to find what kind of devices does Omega 2 support, can I get any sensor from any vendor, does that will work?

    Please reply. Thanks.

  • @kvonion :
    a)The green ones are gpios, there are 18:

    In addition to regular "GPIO", PWM, UART, I2C, SPI, and I2S
    (which are all standard peripheral interfaces) are supported.
    Pins for USB2.0 and UTP Ethernet are also available.

    b)Omega2 pins can only source/sink 3.3v, (NOT any 5 volt). The devices need to compatible with on 3.3 volt. Some devices have 3.0v-5.5v operating range; those can be connected, provided that, you feed them 3.3v ONLY.

    If the device has a fixed operating voltage, it MUST BE 3.3v.

    Here is the documentation home:

  • I would add that in relation to using LEDs, depending on your requirements you can numerous LED off a single PWM pin using Ledchain (Thanks @luz!)

  • @crispyoz Thanks.
    Assume if I have to add few more sensors like 20 temp sensors, 20 buzzers, 20 buttons for each sensors, based on the temp value, there will be 20 different motors which will work as fan, buzz on different conditions, etc., In other words, is there any alternative if I need more than 18 (@tjoseph1 's answer) or I have to use a different Omega2.

    As I am newbie to the pi world is there any video link to help me to understand better?

    Once again, thanks for helping me, I appreciate your help.


  • If you want to interface a lot of devices, you would typically adopt mux/demux technique, with a middle-level "device aggregator".

    See this: https://www.instructables.com/id/Tims-PCA9685-Controller

    One side (the micro-controller -uC- facing side) is I2C, while the "physical device" facing side is PWM. The micro-controller talks to 9685 (device aggregator), which in turn would talk to the devices connected to its 16 channels.

    Note that the above URL has Atmel 8-bit uC/Arduino as the "controlling platform". The point is that, we are making use of the I2C interface which is present in almost any uC .

    Further, the data sheet of the 9685 provided in the above link:
    https://cdn-shop.adafruit.com/datasheets/PCA9685.pdf says that, "The
    PCA9685 operates with a supply voltage range of 2.3 V to 5.5 V and the inputs and outputs are 5.5 V tolerant". So, you can drive it using 3.3v.

    Picking the the right hardware to meet a "specific requirement" is an art, that takes time to get anywhere near the mastery. Getting used to the "datasheet" is the basic requirement. Luckily, the Internet has tons of resources providing implementation details of various project.

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